Bridge

Abstract

To provide a temperature-responsive compound having water-absorbing and dewatering abilities in a balanced manner in an environment where a rubber product is used.SOLUTION: The present invention provides a crosslinked product of a copolymer having a repeat unit A1 represented by formula (A1) and a repeat unit B1 represented by formula (B1), where the repeat unit A1 and the repeat unit B1 are different.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a crosslinked product. [Background technology]

[0002] Polymers known as temperature-responsive polymers have been known to become hydrophobic above a certain temperature and insoluble in water, but become hydrophilic and soluble below that temperature. The temperature at which these properties are exhibited in temperature-responsive polymers is called the lower critical solution temperature (LCST). An example of the temperature-responsive polymer is a homopolymer of N-isopropylacrylamide. Taking advantage of the above properties, thermoresponsive polymers are applied to human medicines and tests, and in such cases, the LCST of the thermoresponsive polymer with water or the like is designed to be, for example, around body temperature or higher.

[0003] On the other hand, a rubber composition used in the tire tread portion of a tire is known in which gel particles of a thermosensitive water-absorbing polymer are blended with rubber, and the thermosensitive water-absorbing polymer is polyacrylamide (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-123018 Summary of the Invention [Problem to be solved by the invention]

[0005] As safety requirements for automobiles increase, there is a demand for further improvements in tire performance on ice and wet grip. In this situation, the present inventors evaluated a rubber composition containing gel particles of a thermosensitive, water-absorbing polymer (three-dimensionally crosslinked between polymers) with reference to Patent Document 1, and found that the gel particles of the thermosensitive, water-absorbing polymer may have a poor balance between water absorption and drainage properties in the usage environment of rubber products such as tires.

[0006] Therefore, an object of the present invention is to provide a temperature-responsive compound that has an excellent balance between water absorption and drainage properties in the environment in which rubber products are used. [Means for solving the problem]

[0007] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a crosslinked product of a copolymer having two specific repeating units.

[0008] [1] A crosslinked copolymer having a repeating unit A1 represented by the following formula (A1) and a repeating unit B1 represented by the following formula (B1), wherein the repeating unit A1 and the repeating unit B1 are different from each other. [ka] In formula (A1), R A1 each independently represents a hydrogen atom or a branched alkyl group having 3 to 10 carbon atoms; R A1 At least one of the groups is the alkyl group, and in formula (B1), R B1 each independently represents a hydrogen atom or a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms; R B1 At least one of the groups is the alkyl group. [2] Lower critical solution temperature of the crosslinked product T or the lower critical solution temperature of the copolymer C and each independently range from -10°C to +60°C. [3] The homopolymer of the repeating unit A1 has a lower critical solution temperature A and / or the homopolymer of the repeating unit B1 has a lower critical solution temperature BThe crosslinked product according to [1] or [2], [4] The homopolymer of the repeating unit A1 has a lower critical solution temperature A and the homopolymer of the repeating unit B1 has a lower critical solution temperature B and the lower critical solution temperature B is the lower critical solution temperature A is lower than, or The homopolymer of the repeating unit A1 has a lower critical solution temperature A and the homopolymer of the repeating unit B1 has a lower critical solution temperature B The crosslinked product according to any one of [1] to [3], which does not have any of the following: [5] In equation (A1), one of R A1 is a hydrogen atom, and the other R A1 represents a branched alkyl group having 3 to 10 carbon atoms. [6] The crosslinked product according to any one of [1] to [5], wherein the repeating unit A1 contains a repeating unit of N-isopropylacrylamide. [7] In equation (B1), one of R B1 is a hydrogen atom, and the other R B1 represents a linear or branched alkyl group having 4 to 10 carbon atoms, or R B1 each independently represents a linear or branched alkyl group having 1 to 10 carbon atoms. [8] The crosslinked product according to any one of [1] to [7], wherein the repeating unit B1 contains a repeating unit of N-tert-butylacrylamide or N,N-dimethylacrylamide. [9] The crosslinked product according to any one of [1] to [8], which is a random copolymer.

[0009]

[10] A compounding agent for rubber, comprising the crosslinked product according to any one of [1] to [9]. [Effects of the Invention]

[0010] The crosslinked product of the present invention has an excellent balance between water absorption and drainage properties in the environment in which rubber products are used. DETAILED DESCRIPTION OF THE INVENTION

[0011] The crosslinked product of the present invention will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to". In this specification, each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. In this specification, the repeating unit A1 represented by formula (A1) may be simply referred to as “A1.” The same applies to the repeating unit B1 represented by formula (B1), etc.

[0012] [Crosslinked product] The crosslinked product of the present invention is a crosslinked product of a copolymer having a repeating unit A1 represented by the following formula (A1) and a repeating unit B1 represented by the following formula (B1), provided that in the present invention, the repeating unit A1 and the repeating unit B1 are different. [ka] In formula (A1), R A1 each independently represents a hydrogen atom or a branched alkyl group having 3 to 10 carbon atoms; R A1 At least one of the groups is the above-mentioned alkyl group (branched and having 3 to 10 carbon atoms). In formula (B1), R B1 each independently represents a hydrogen atom or a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms; R B1 At least one of the groups is the above-mentioned alkyl group (linear having 1 to 10 carbon atoms or branched having 3 to 10 carbon atoms).

[0013] It is believed that the crosslinked product of the present invention has such a structure and therefore exhibits the above-mentioned effects. The reason for this is not clear, but is presumed to be as follows. Typically, tires are used in a variety of locations, including cold and tropical regions, and the temperature of the tire's operating environment also varies. However, if there is a large difference between the temperature of the tire's operating environment and the lower critical solution temperature of the thermosensitive water-absorbing polymer or its crosslinked product contained in the tire, the thermosensitive water-absorbing polymer or its crosslinked product is thought to be unable to exhibit its temperature responsiveness. For example, if a tire used in a cold region below 0°C contains a crosslinked thermosensitive water-absorbing polymer with an LCST close to human body temperature, the crosslinked thermosensitive water-absorbing polymer will absorb water in the above temperature environment, but will not release water unless the operating environment temperature reaches or exceeds the LCST. If water is not released from the crosslinked thermosensitive water-absorbing polymer as described above, tire performance, such as ice performance and wet grip performance, is expected to deteriorate. On the other hand, the LCST that the crosslinked product of the present invention can have can be set in various ranges and in detail by combining the repeating units A1 and B1 in the copolymer (main chain) that constitutes the crosslinked product of the present invention. As described above, the crosslinked product of the present invention is considered to be a temperature-responsive compound having an excellent balance between water absorption and drainage. As a result, with the crosslinked product of the present invention, it is possible to select a crosslinked product suitable for a rubber product such as a tire depending on the environment in which it will be used.

[0014] Furthermore, since the copolymer in the crosslinked product of the present invention is crosslinked to form, for example, a network structure, when the crosslinked product of the present invention comes into contact with water at a temperature below the LCST with water, the crosslinked product of the present invention can absorb water and become gel-like. In other words, under the above conditions, the crosslinked product of the present invention in a rubber product dissolves in water and does not flow out of the rubber product with water. Furthermore, when the crosslinked product of the present invention is in a gel state as described above and the ambient temperature of use is changed to a temperature above the LCST with water, the crosslinked product of the present invention changes from a gel state (a state in which the degree of hydrophilicity / hydrophobicity is more hydrophilic) to a state in which the degree of hydrophilicity / hydrophobicity is more hydrophobic, allowing water to be expelled from the crosslinked product of the present invention. In this way, it is believed that the crosslinked product of the present invention does not flow out of the rubber product even when the rubber product is wet with water, but remains within the rubber product.

[0015] In the crosslinked product of the present invention, the copolymer having the repeating unit A1 and the repeating unit B1 is crosslinked via a crosslinking moiety. In the present invention, the term "copolymer having repeating units A1 and B1" refers to a chain (main chain) having at least repeating units A1 and B1 in the crosslinked product of the present invention. The term "crosslinked product" refers to the entire crosslinked product of the present invention. A part of the crosslinked portion may be incorporated into the copolymer to form a part of the copolymer. The crosslinked product of the present invention may be a copolymer (as a whole) having repeating units A1 and B1 and a crosslinked portion. An example of an embodiment of the crosslinked product of the present invention is a network structure. Furthermore, the crosslinked product of the present invention can be temperature responsive and can have an LCST with a liquid (for example, water). The crosslinked product of the present invention is capable of absorbing a liquid such as water and maintaining that state (also referred to as a swollen state or a gel state) under temperature conditions below the LCST that the crosslinked product of the present invention may have, due to the crosslinking of the copolymer (having the repeating unit A1 and the repeating unit B1).

[0016] (Lower critical solution temperature of cross-linked material T ) Lower critical solution temperature of the crosslinked product of the present invention T From the viewpoint of obtaining a more excellent effect of the present invention, the temperature is preferably from -10°C to +60°C, more preferably from -10°C to +40°C, and even more preferably from -10°C or higher to lower than +20°C.

[0017] Lower critical solution temperature of the crosslinked product of the present invention T Measurement method The crosslinked product of the present invention was mixed with pure water to adjust the concentration of the crosslinked product of the present invention to 0.5% by mass in a mixture of the crosslinked product of the present invention and pure water (total amount of mixture: 100 g), and the mixture was placed in a quartz cell with an optical path length of 1 cm. The temperature of the mixture was raised from 0°C at a rate of 1°C / min, while the transmittance of light at a wavelength of 500 nm through the mixture was measured with a spectrophotometer (Hitachi UH-5300). From the measurement results, the temperature corresponding to the average value between the approximately maximum value of transmittance (for example, the transmittance immediately before the transmittance suddenly drops) and the approximately minimum value of transmittance was determined by the midpoint method, and this was determined as the LCST (lower critical solution temperature) of the crosslinked product of the present invention (with water). T ) was decided. In the present specification, the lower critical solution temperature of a copolymer (not crosslinked) having the repeating unit A1 and the repeating unit B1 is C , the lower critical solution temperature of the homopolymer (uncrosslinked) of the repeating unit A1 A and the lower critical solution temperature of the homopolymer (uncrosslinked) of the repeating unit B1 B The method for measuring the lower critical solution temperature is T The measurement method is the same as that of

[0018] (molar ratio of A1 to B1) From the viewpoint of achieving superior effects of the present invention, the molar ratio (A1:B1) of the repeating units A1 to B1 constituting the crosslinked product of the present invention is preferably 1:99 to 99:1, more preferably 10:90 to 80:20, even more preferably 10:90 to 75:25, and even more preferably 25:75 to 60:40.

[0019] (random copolymer) The crosslinked product of the present invention is preferably a random copolymer, from the viewpoint of easily exhibiting temperature responsiveness and achieving better effects of the present invention.

[0020] [Copolymer] The copolymer (main chain) constituting the crosslinked product of the present invention has repeating units A1 and B1, provided that in the present invention, the repeating units A1 and B1 are different. The repeating unit A1 is not particularly limited as long as it has a structure that satisfies the above formula (A1), and may be a single unit or a combination of two or more units. The same applies to the repeating unit B1.

[0021] (Lower critical solution temperature of copolymer C ) Lower critical solution temperature of the copolymer of the crosslinked product of the present invention C From the viewpoint of obtaining a more excellent effect of the present invention, the temperature is preferably from -10°C to +60°C, more preferably from -10°C to +40°C, and even more preferably from -10°C or higher to lower than +20°C. In this specification, the lower critical solution temperature of the copolymer C indicates the lower critical solution temperature of the copolymer alone, that is, the copolymer having a repeating unit A1 represented by formula (A1) and a repeating unit B1 represented by formula (B1) and is not crosslinked.

[0022] Furthermore, the copolymer contained in the crosslinked product of the present invention is preferably a random copolymer, from the viewpoint that temperature responsiveness is easily exhibited and the effects of the present invention are more excellent.

[0023] [Bridge part] The crosslinked product of the present invention has a crosslinked portion, and therefore, the crosslinked product of the present invention has a lower critical solution temperature (CTC) of 1000 ppm or less with water. T When the crosslinked product of the present invention comes into contact with water under a temperature condition below 100°C, it can absorb water and become gel-like. The crosslinked moieties constituting the crosslinked product of the present invention can crosslink the copolymer between molecules. The copolymer may be crosslinked intramolecularly. The structure of the crosslinked moiety is not particularly limited as long as it is at least divalent. Examples include a divalent or higher hydrocarbon group, an ester bond, an amide bond, an ether bond, or a combination thereof. The crosslinked portion may be bonded to the repeating unit A1 or B1 via a group (--CC--) resulting from the cleavage of at least two ethylenically unsaturated bonds, thereby constituting a part of the copolymer. In the crosslinked product of the present invention, the crosslinked moiety can be constituted by, for example, a monomer having a plurality of ethylenically unsaturated bonds, as will be described later. However, one of the preferred embodiments of the crosslinked product of the present invention is one in which the crosslinked product has almost no unreacted ethylenically unsaturated bonds derived from the above-mentioned monomers.

[0024] An example of the structure of the crosslinked portion is a repeating unit C1 represented by the following formula (C1). [ka]

[0025] In formula (C1), R 1 each independently represents a hydrogen atom or an alkyl group, and X 1 each independently represents an ester bond or an amide bond, R 2 represents a hydrocarbon group, an oxyalkylene group or a polyoxyalkylene group.

[0026] ·R 1 The alkyl group may, for example, be a methyl group.

[0027] ·R 2 R 2 The hydrocarbon group as mentioned above is not particularly limited as long as it is divalent. For example, it may be a hydrocarbon group having 1 to 20 carbon atoms. Examples of the hydrocarbon group include an alkylene group and a phenylene group. R 2 Examples of the oxyalkylene group as the alkyl group include an oxyethylene group and an oxypropylene group. R 2 Examples of the polyoxyalkylene group include a polyoxyethylene group and a polyoxypropylene group. The degree of polymerization of the polyoxyalkylene group is, for example, 2 to 10. R 2From the viewpoint of achieving better effects of the present invention, alkylene groups having 1 to 12 carbon atoms are preferred, and alkylene groups having 6 to 12 carbon atoms are more preferred because they have excellent resistance to acids in addition to the above viewpoint.

[0028] In formula (C1), the moiety shown below can constitute a part of the copolymer. * in the following formula represents X in formula (C1). 1 represents the bonding position with [ka]

[0029] The crosslinked portion is preferably a repeating unit represented by the following formula (c-1), from the viewpoint of achieving better effects of the present invention (particularly absorbency) and suppressing dissolution and / or outflow into water. [ka] In formula (c-1), R 1 , R 2 is R in formula (C1) 1 , R 2 and the same respectively.

[0030] (Ratio of cross-linked parts) The proportion of the crosslinked moiety (e.g., the above formula (C1)) constituting the crosslinked product of the present invention is preferably 0.0001 to 0.5 mol, and more preferably 0.01 to 0.3 mol, per mol of the total number of moles of repeating units A1 and B1, from the viewpoints of achieving better effects of the present invention (particularly water absorbency), suppressing dissolution and / or outflow into water, and rapid manifestation of LCST (speed of phase transition).

[0031] [Repeating unit A1] In the present invention, the repeating unit A1 is a repeating unit represented by the above formula (A1). [ka] In formula (A1), R A1each independently represents a hydrogen atom or a branched alkyl group having 3 to 10 carbon atoms, and two R A1 At least one of the above is a branched alkyl group having a carbon number of 3 to 10. The branched alkyl group may form a ring structure.

[0032] Branched alkyl groups with 3 to 10 carbon atoms Examples of branched alkyl groups having 3 to 10 carbon atoms include an isopropyl group, an isobutyl group, a tert-butyl group, and a cyclohexyl group.

[0033] A1 preferred embodiment From the viewpoint of achieving a more excellent effect of the present invention, A1 is A1 is a hydrogen atom, and the other R A1 preferably represents a branched alkyl group having 3 to 10 carbon atoms, and one R A1 is a hydrogen atom, and the other R A1 More preferably, represents an isopropyl group or a tert-butyl group.

[0034] From the viewpoint of achieving better effects of the present invention, the repeating unit A1 preferably contains a repeating unit of N-isopropylacrylamide.

[0035] Homopolymer of repeating unit A1 From the viewpoint of achieving a more excellent effect of the present invention, A1 is a repeating unit having a homopolymer of the repeating unit A1 having a lower critical solution temperature T A It is preferred that the compound has the following structure:

[0036] (lower limit critical solution temperature A ) Lower critical solution temperature of the homopolymer of the repeating unit A1 constituting the copolymer of the crosslinked product of the present invention A From the viewpoint of obtaining a more excellent effect of the present invention, the temperature is preferably +5°C or higher, and more preferably +10 to +50°C. In this specification, the lower critical solution temperature Aindicates the lower critical solution temperature of a homopolymer of the repeating unit A1 represented by formula (A1). Lower critical solution temperature of homopolymer of N-isopropylacrylamide A is 32°C.

[0037] [Repeating unit B1] In the present invention, the repeating unit B1 is a repeating unit represented by the above formula (B1). [ka] In formula (B1), R B1 each independently represents a hydrogen atom or a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms, and two R B1 At least one of the groups is a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms.

[0038] Straight-chain alkyl groups with 1 to 10 carbon atoms Examples of the linear alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, and a decyl group.

[0039] Branched alkyl groups R B1 As the branched alkyl group, the above-mentioned R A1 Examples include the same branched alkyl groups having 3 to 10 carbon atoms as those mentioned above.

[0040] R in formula (B1) B1 combination of R in formula (B1) B1 In view of the fact that the effects of the present invention are more excellent, the combination of B1 is a hydrogen atom, and the other R B1 represents a linear or branched alkyl group having 4 to 10 carbon atoms, or R B1 are each independently a linear or branched alkyl group having 1 to 10 carbon atoms is preferred. An example of a repeating unit that falls under the above combination 1 is a repeating unit of N-tert-butylacrylamide. An example of a repeating unit that falls under the above combination 2 is a repeating unit of N,N-dimethylacrylamide.

[0041] From the viewpoint of achieving better effects of the present invention, the repeating unit B1 preferably contains a repeating unit of N-tert-butylacrylamide or N,N-dimethylacrylamide.

[0042] From the viewpoint of achieving a more excellent effect of the present invention, it is preferable that the repeating unit B1 contains a repeating unit of the above combination 1, and one of R B1 is a hydrogen atom, and the other R B1 It is more preferable that the repeating unit is a branched alkyl group having 4 to 10 carbon atoms, and it is even more preferable that the repeating unit is N-tert-butylacrylamide.

[0043] (lower limit critical solution temperature B ) The homopolymer of the repeating unit B1 constituting the copolymer of the crosslinked product of the present invention has a lower critical solution temperature B If the lower critical solution temperature B From the viewpoint of obtaining a more excellent effect of the present invention, the temperature is preferably −20 to +25° C. or less. In this specification, the lower critical solution temperature B indicates the lower critical solution temperature of a homopolymer of the repeating unit B1 represented by formula (B1). Lower critical solution temperature of N-tert-butylacrylamide homopolymer B is below 0°C. The homopolymer of N,N-dimethylacrylamide does not have a lower critical solution temperature.

[0044] (lower limit critical solution temperature A and the lower critical solution temperature B (Relationship) The homopolymer of repeating unit A1 has a lower critical solution temperature A When the repeating unit B1 has a lower critical solution temperature B may or may not have. Lower critical solution temperature A and the lower critical solution temperature B For example, the relationship is The homopolymer of repeating unit A1 has a lower critical solution temperature A The homopolymer of the repeating unit B1 has a lower critical solution temperature B and has a lower critical solution temperature B is the lower critical solution temperature A is lower than The homopolymer of repeating unit A1 has a lower critical solution temperature A and the homopolymer of the repeating unit B1 has a lower critical solution temperature B In some cases, the above-mentioned feature is not present. Lower critical solution temperature A and the lower critical solution temperature B If the relationship is the former, the lower critical solution temperature T or lower critical solution temperature C For example, the lower critical solution temperature A and the lower critical solution temperature B The temperature can be adjusted to the range between the lower critical solution temperature A and the lower critical solution temperature B A specific example of the former relationship is when the repeating unit A1 is a repeating unit based on NIPAM and the repeating unit B1 is a repeating unit based on NTBAM. Lower critical solution temperature A and the lower critical solution temperature B If the relationship is the latter, the lower critical solution temperature T or lower critical solution temperature C For example, the lower critical solution temperature A The lower critical solution temperature can be adjusted higher than A and the lower critical solution temperature BA specific example of the latter relationship is when the repeating unit A1 is a repeating unit based on NIPAM and the repeating unit B1 is a repeating unit based on DMAAm.

[0045] (Manufacturing method) The crosslinked product of the present invention can be produced, for example, by polymerizing monomers having ethylenically unsaturated bonds corresponding to the repeating units A1, B1, and crosslinking moieties, respectively. The monomers corresponding to the repeating units A1 and B1 are acrylamide compounds. The monomers that can constitute the crosslinking moieties can have multiple ethylenically unsaturated bonds. The monomers corresponding to the repeating unit A1 and the monomers corresponding to the repeating unit B1 are different. The polymerization is carried out at a temperature lower than the critical solution temperature of the crosslinked product of the present invention, so that the effect of the present invention is more excellent. T Radical polymerization is preferred from the viewpoint that the above-mentioned effect is easily exhibited.

[0046] Monomers that can constitute repeating unit A1 Examples of monomers that can constitute the repeating unit A1 include N-alkylacrylamides in which one branched alkyl group having 3 to 10 carbon atoms is bonded to a nitrogen atom, such as N-isopropylacrylamide (NIPAM), N-isobutylacrylamide, N-tert-butylacrylamide (NTBAM), 2-ethylhexylacrylamide, and N-cyclohexylacrylamide; Examples include N,N-dialkylacrylamides in which two branched alkyl groups having 3 to 10 carbon atoms are bonded to a nitrogen atom, such as N,N-diisopropylacrylamide. The monomer capable of constituting the repeating unit A1 is one which has a higher effect of the present invention and has a lower critical solution temperature of the crosslinked product of the present invention. T From the viewpoint of facilitating the expression of the above, it is preferable to include N-alkylacrylamide in which one branched alkyl group having 3 to 10 carbon atoms is bonded to a nitrogen atom, and it is more preferable to include N-isopropylacrylamide (NIPAM).

[0047] Monomers that can constitute repeating unit B1 Examples of monomers that can constitute the repeating unit B1 include N-alkylacrylamide, in which one linear or branched alkyl group having 4 to 10 carbon atoms is bonded to the nitrogen atom; B1 and N,N-dialkylacrylamide, in which each independently represents a linear or branched alkyl group having 1 to 10 carbon atoms. The monomer capable of constituting the repeating unit B1 is a monomer that has a lower critical solution temperature than that of the crosslinked product of the present invention and is excellent in the effect of the present invention. T From the viewpoint of facilitating the expression of the above, it is preferable that the compound contains the above-mentioned N-alkylacrylamide or N,N-dialkylacrylamide, More preferably, the compound includes an N-alkylacrylamide or an N,N-dialkylacrylamide in which one branched alkyl group having 4 to 10 carbon atoms is bonded to a nitrogen atom, More preferably, it contains Nt-butylacrylamide (NTBAM) or N,N-dimethylacrylamide.

[0048] Monomers that can form crosslinking moieties Examples of the monomer that can constitute the crosslinking moiety include N,N'-alkylenebis(meth)acrylamides such as N,N'-methylenebis(meth)acrylamide; alkylenediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, monopropylene glycol diacrylate, 1,4-butanediol di(meth)acrylate, and 1,10-bis((meth)acryloyloxy)decane; Examples thereof include polyoxyalkylene diol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and polypropylene glycol di(meth)acrylate.

[0049] In the present invention, the molar ratio of the monomer capable of constituting the repeating unit A1 to the monomer capable of constituting the repeating unit B1 is reflected in the molar ratio of the repeating units A1 and B1. The ratio of the monomer capable of forming the crosslinked moiety to the total number of moles of the monomer capable of forming the repeating unit A1 and the monomer capable of forming the repeating unit B1 is reflected in the ratio of the crosslinked moiety.

[0050] Examples of methods for producing the crosslinked product of the present invention include a method of radically polymerizing a monomer capable of constituting the repeating unit A1, a monomer capable of constituting the repeating unit B1, and a monomer capable of constituting the crosslinked moiety in an organic solvent such as methyl ethyl ketone in the presence of an initiator such as azobisisobutyronitrile at 40 to 100°C. The amount of initiator used is preferably 0.0001 to 0.05 mol, more preferably 0.001 to 0.03 mol, per mol of the total number of moles of repeating units A1, B1 and monomers corresponding to the crosslinking moiety. After polymerization, the crosslinked product of the present invention can be purified, for example, by adding water to the reaction solution to remove unreacted raw materials and then vacuum drying.

[0051] [Application] The crosslinked product of the present invention is a temperature-responsive compound having excellent water absorption and drainage properties as described above, and is therefore useful, for example, as a compounding agent for rubber (a material that can be used for rubber). In the present invention, the lower critical solution temperature of the crosslinked product of the present invention can be controlled by selecting the repeating units A1 and B1 contained in the crosslinked product of the present invention, and further, if necessary, by selecting, for example, the molar ratio of the repeating units A1 and B1. T The temperature can be adjusted according to the environment in which the rubber product is used.

[0052] [Rubber compounding agents] The compounding agent for rubber of the present invention is a compounding agent for rubber containing the crosslinked product of the present invention.

[0053] (Crosslinked product) The crosslinked product contained in the compounding agent for rubber of the present invention is not particularly limited as long as it is the crosslinked product of the present invention.

[0054] (rubber) There are no particular restrictions on the rubber to which the compounding agent for rubber of the present invention can be applied. The rubber compounding agent of the present invention may be applied to a rubber composition, such as a rubber composition for tires, specifically a rubber composition for tire treads and a rubber composition for studless tires. [Example]

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0056] [Production of crosslinked product] Each crosslinked product was produced as follows. Here, specific crosslinked products 1 to 8 are crosslinked products of copolymers having two specific repeating units, and therefore correspond to the crosslinked products of the present invention. Details of each crosslinked product are shown in Table 1. Table 1 shows the mole percentage of each repeating unit in the total of repeating units A1 and B1, the ratio of repeating unit C1 (crosslinking agent) (the ratio is the number of moles of repeating unit C1 in the crosslinking portion per mole of repeating units A1 and B1 combined (*1 in Table 1)), the amount of initiator used (the amount is the number of moles of initiator per mole of repeating units A1, B1 and the monomers corresponding to the crosslinking portion combined (*2 in Table 1)), and the lower critical solution temperature of each crosslinked product (the entire compound finally obtained). T , lower critical solution temperature of the copolymer C Shows. On the other hand, Comparative Compound 1 is a crosslinked product of NIPAM homopolymer and therefore does not fall under the crosslinked product of the present invention. Comparative Compound 2 is a NIPAM homopolymer and is not a crosslinked product, so does not fall under the crosslinked product of the present invention. Comparative Compound 3 is a NTBAM homopolymer and is not a crosslinked product, so does not fall under the crosslinked product of the present invention.

[0057] <Specific crosslinked product 1> In methyl ethyl ketone (MEK), 1.0 g of N-isopropylacrylamide (NIPAM), 0.12 g of Nt-butylacrylamide (NTBAM), and 36 mg of N,N'-methylenebis(acrylamide) (hereafter referred to as MBAAm) as crosslinker 1 were polymerized by radical polymerization using 15 mg of azobisisobutyronitrile (AIBN) as an initiator (60°C, 8 hours). The mixing ratio of NIPAM to NTBAM (molar ratio of NIPAM / NTBAM) was 90 / 10. After the polymerization, a large amount of water was added to the reaction solution to remove unreacted raw materials, and the mixture was dried in vacuum at 80° C. for 24 hours.

[0058] As a result, a crosslinked product represented by the following formula X was obtained. The crosslinked product represented by the following formula X is a copolymer having repeating units a-1 represented by the following formula (a-1) and repeating units b-1 represented by the following formula (b-1) arranged randomly, which are crosslinked with repeating units c-1 represented by the following formula (c-1). In the following formula X, m is the number of repeating units a-1, n is the number of repeating units b-1, and o is the number of repeating units c-1. The * in repeating unit c-1 represents a bond with another repeating unit a-1 or repeating unit b-1, but these are omitted as they are the same as those already shown in formula X. The obtained crosslinked product is referred to as specific crosslinked product 1.

[0059] Specific Crosslinked Products 2 to 5 described below can also be represented by the following formula X. The repeating unit a-1 contained in Specific Crosslinked Products 1 to 5 was formed from NIPAM, and the repeating unit b-1 was formed from NTBAM. Furthermore, the copolymers constituting the specific cross-linked materials 1 to 8 described below are random copolymers, and the specific cross-linked materials 1 to 8 themselves are also random copolymers. As shown in the evaluation of water absorbency described later, when specific crosslinked materials 1 to 8 were immersed in a solvent (water), they did not dissolve in water but swelled (gelled). This suggests that a crosslinking agent was introduced into specific crosslinked materials 1 to 8, and specific crosslinked materials 1 to 8 were crosslinked to form a network structure.

[0060] [ka]

[0061] <Specific crosslinked product 2> A crosslinked product represented by the above formula X was obtained in the same manner as in the above-mentioned specific crosslinked product 1, except that the mixing ratio (molar ratio) of NIPAM and NTBAM was changed to 75 / 25 and the amount of crosslinker 1 was changed. The obtained crosslinked product is designated as specific crosslinked product 2.

[0062] <Specific crosslinked product 3> A crosslinked product represented by the above formula X was obtained in the same manner as in the above-mentioned specific crosslinked product 1, except that the mixing ratio (molar ratio) of NIPAM and NTBAM was changed to 50 / 50 and the amount of crosslinker 1 was changed. The obtained crosslinked product is designated as specific crosslinked product 3.

[0063] <Specific crosslinked material 4> A crosslinked product represented by the above formula X was obtained in the same manner as in the above-mentioned specific crosslinked product 1, except that the mixing ratio (molar ratio) of NIPAM and NTBAM was changed to 10 / 90 and the amount of crosslinker 1 was changed. The obtained crosslinked product is designated as specific crosslinked product 4.

[0064] (Comparative Compound 1) A crosslinked product was obtained in the same manner as in the above-mentioned specific crosslinked product 1, except that NTBAM was not used and the amount of crosslinker 1 was changed. The obtained crosslinked product is designated as comparative compound 1.

[0065] (Comparative Compound 2) A homopolymer of NIPAM was obtained in the same manner as in the above-mentioned specific crosslinked product 1, except that NTBAM and MBAAm were not used. The obtained compound is designated as comparative compound 2.

[0066] (Comparative compound 3) A homopolymer of NTBAM was obtained in the same manner as in the above-mentioned specific crosslinked product 1, except that NIPAM and MBAAm were not used. The obtained compound is designated as comparative compound 3.

[0067] <Specific crosslinked material 5> A crosslinked product was obtained in the same manner as in the above-mentioned specific crosslinked product 1, except that crosslinking agent 1 (MBAAm) was changed to 50 mg of crosslinking agent 2 (ethylene glycol diacrylate). The obtained crosslinked product is designated as specific crosslinked product 5.

[0068] <Specific crosslinked product 6> A crosslinked product was obtained in the same manner as in the above-mentioned specific crosslinked product 2, except that the mixture of NIPAM and NTBAM was replaced with a mixture of NIPAM and N,N-dimethylacrylamide (DMAAm), and the mixing ratio (molar ratio of NIPAM / N,N-dimethylacrylamide) was changed to 80 / 20. The obtained crosslinked product is designated as specific crosslinked product 6. The structure of specific crosslinked product 6 is the same as that of formula X above, except that the repeating unit b-1 represented by formula (b-1) is a repeating unit derived from N,N-dimethylacrylamide.

[0069] <Specific crosslinked product 7> A crosslinked product was obtained in the same manner as the above-mentioned specific crosslinked product 6, except that the mixing ratio (molar ratio) of NIPAM and DMAAm was changed to 60 / 40. The obtained crosslinked product is designated as specific crosslinked product 7. The structure of specific crosslinked product 7 is the same as that of formula X above, except that the repeating unit b-1 represented by formula (b-1) is a repeating unit derived from N,N-dimethylacrylamide.

[0070] <Specific crosslinked product 8> A crosslinked product was obtained in the same manner as the above-mentioned specific crosslinked product 6, except that the mixing ratio (molar ratio) of NIPAM and DMAAm was changed to 40 / 60. The obtained crosslinked product is designated as specific crosslinked product 8. The structure of specific crosslinked product 8 is the same as that of formula X above, except that the repeating unit b-1 represented by formula (b-1) is a repeating unit derived from N,N-dimethylacrylamide.

[0071] In each example, polymerization was carried out in the same manner as above except that no crosslinking agent was used, and a copolymer (or homopolymer) was obtained separately from the specific crosslinked product.

[0072] [Evaluation of the crosslinked product] The crosslinked products produced as described above were evaluated as follows, and the results are shown in Table 1. <Water absorption / drainage properties> ·Water absorption 1.0 g of each crosslinked product, which had been produced as described above and then vacuum-dried, was immersed in 100 g of water and left at +2°C for 1 hour to swell the crosslinked product. After 1 hour, the state of the crosslinked product (whether it had gelled or dissolved) was visually confirmed.

[0073] ·Water absorption rate (residual water rate) Next, each of the swollen crosslinked products was filtered, and the weight W of the filtered gel-like crosslinked product (swollen gel) was calculated. gel Next, the swollen gel was again dried in vacuum at 60°C for 24 hours (the pressure during vacuum drying was 0.1 MPa), and the weight W of the crosslinked product after drying was measured. dry (g) and obtain the value W gel , W dry The water absorption rate (residual water rate) was calculated by applying the above to the following formula. Water absorption rate (residual water rate) [g / g]=(W gel -W dry ) / W dry

[0074] Evaluation criteria for water absorption and drainage In the present invention, when a crosslinked product was left in water at +2°C for 1 hour, and the crosslinked product swelled (gelled) and had a water absorption rate (residual water rate) of less than 30, the crosslinked product was evaluated as having excellent water absorption and drainage properties. In the above cases, when the water absorption rate (residual water rate) was less than 30, the drainage property was evaluated as being better. On the other hand, if a crosslinked product (or an uncrosslinked product) was left in water at +2°C for 1 hour and no gelation was observed (for example, the crosslinked product (or an uncrosslinked product) was completely dissolved in water), the water absorbency was evaluated as poor. Note that if the crosslinked product (or an uncrosslinked product) was dissolved in water and no gelation was observed, the compound had no water absorbency, and if the compound was dried at a temperature higher than its LCST, the water absorption rate (residual water rate) after drying would be 0. Furthermore, when the water absorption rate (residual water rate) was 30 or more, the crosslinked product was evaluated as having poor drainage properties.

[0075] <Lower critical solution temperature> The lower critical solution temperature of each crosslinked product prepared as above T and the lower critical solution temperature of the copolymer of the crosslinked product C The lower critical solution temperature is shown in Table 1. T and lower critical solution temperature C The measurement method is as described above. Lower critical solution temperature of Comparative Example 2 C The column shows the lower critical solution temperature of Comparative Compound 2 (homopolymer). C The same is true for columns.

[0076] [Table 1]

[0077] The results shown in Table 1 indicate that Comparative Compound 1, which is a crosslinked product of NIPAM homopolymer, had poor drainage properties. Comparative Compound 2, which is simply a NIPAM homopolymer and is not a crosslinked product, did not absorb water. Comparative Compound 3, which is a simple NTBAM homopolymer and is not a cross-linked product, did not absorb water.

[0078] On the other hand, the crosslinked product of the present invention and the compounding agent for rubber of the present invention have an excellent balance of water absorption and drainage properties in the environment in which rubber products such as tires are used.

Claims

1. A compounding agent for rubber, comprising a crosslinked product of a copolymer having a repeating unit A1 represented by the following formula (A1) and a repeating unit B1 represented by the following formula (B1), wherein the crosslinked product has a repeating unit C1 represented by the following formula (C1) as a crosslinked moiety, and the crosslinked product has only the repeating unit A1, the repeating unit B1, and the repeating unit C1 as repeating units, provided that the repeating unit A1 and the repeating unit B1 are different. 【Chemistry 1】 In formula (A1), R Ａ１ each independently represents a hydrogen atom or a branched alkyl group having 3 to 10 carbon atoms; R Ａ１ At least one of the groups is the alkyl group, and in formula (B1), R Ｂ１ each independently represents a hydrogen atom or a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms; R Ｂ１ At least one of the groups is the alkyl group. 【Chemistry 2】 In formula (C1), R 1 s each independently represent a hydrogen atom or an alkyl group, X 1 s each independently represent an ester bond or an amide bond, and R 2 represents a hydrocarbon group, an oxyalkylene group, or a polyoxyalkylene group.

2. The lower critical solution temperature of the crosslinked product Ｔ or a lower critical solution temperature of a copolymer having only the repeating unit A1 and the repeating unit B1 C and each independently range from -10°C to +60°C.

3. The homopolymer of the repeating unit A1 has a lower critical solution temperature Ａ and / or the homopolymer of the repeating unit B1 has a lower critical solution temperature Ｂ The compounding agent for rubber according to claim 1 or 2, which has the formula:

4. The homopolymer of the repeating unit A1 has a lower critical solution temperature Ａ and the homopolymer of the repeating unit B1 has a lower critical solution temperature Ｂ and the lower critical solution temperature Ｂ is the lower critical solution temperature Ａ is lower than, or The homopolymer of the repeating unit A1 has a lower critical solution temperature Ａ and the homopolymer of the repeating unit B1 has a lower critical solution temperature Ｂ The compounding agent for rubber according to any one of claims 1 to 3, which does not have any of the following:

5. In formula (A1), one R Ａ１ is a hydrogen atom, and the other R Ａ１ The compounding agent for rubber according to any one of claims 1 to 4, wherein represents a branched alkyl group having 3 to 10 carbon atoms.

6. The compounding agent for rubber according to any one of claims 1 to 5, wherein the repeating unit A1 includes a repeating unit derived from N-isopropylacrylamide.

7. In formula (B1), one R Ｂ１ is a hydrogen atom, and the other R Ｂ１ represents a linear or branched alkyl group having 4 to 10 carbon atoms, or R Ｂ１ The compounding agent for rubber according to any one of claims 1 to 6, wherein each independently represents a linear or branched alkyl group having 1 to 10 carbon atoms.

8. The compounding agent for rubber according to any one of claims 1 to 7, wherein the repeating unit B1 includes a repeating unit derived from N-tert-butylacrylamide or N,N-dimethylacrylamide.

9. A rubber compounding agent according to any one of claims 1 to 8, wherein the cross-linked product is a random copolymer.

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